Question

Can any one Give the example for

 Boolean_conversions Using  reinterpret_cast<>

Iam getting the execution failure..Any one explain ..

Ex:

   void Boolean_Conversions()
     {
         bool b = 0;
         int *i = reinterpret_cast<int*> (&b);
  // iam expecting as *i is 0/false    ,but it is showing runtime error          
     }

Edit:
In ISO Standard
Section $5.2.10, para 1:

      "The result of the expression reinterpret_cast<T>(v) is the
  result of converting the expression v to type T. If T is a
  reference type, the result is an lvalue; otherwise, the re
  sult is an rvalue and the l-value to r-value (4.1), array
  to pointer (4.2), and function to pointer (4.3) standard c
  onversions are performed on the the expression v. Types sh
  all not be defined in a reinterpret_cast."

From this Iam trying ..I did many conversions ..like Array_to_Pointer,Function_To_Pointer,Integral/Pointer_Conversions ,etc…But i don’t know why it is failing For Boolean Conversions.

Can any one tell why it is failing ..Otherwise Tell the Boolean COnversions using reinterpret_cast.

Mostly It is Giving Run time failure in G++.CC/EDG/COdepad..etc compilers

Please Explain

Answer 1

No, the output is not defined. Note that the conversion is undefined.

On my machine *i = 0xcccccc00

Note the lsb which is 00

which corresponds to the value of the bool variable initialized with 0(false). The byte pattern in the other three bytes (assuming the size of int as 32-bits) is completely unspecified and depends on what is there in that memory/endianness etc.

Technically, however that is an undefined behavior because we are deferencing a memory location (all of) which we did not reserve/allocate.